A golf ball comprises a core and a cover surrounding the core. In a conventional method for manufacturing the golf ball, a core material is kneaded, rolled out thin like a piece of paper, compressed, cut to have a core size, and then imprinted any spherical core shape. Next, the spherical core is covered with a cover in a mold, thereby manufacturing the so-called two-piece golf ball. This process may be repeated to manufacture a three-piece golf ball, a four-piece golf ball, a five-piece golf ball or the like.
Thereafter, the mold seam of the golf ball is polished, and the golf ball is marked with a logo and coated with a coating material, followed by drying, thereby obtaining a commercially available golf ball.
Herein, materials for the golf ball cover, particularly an ionomer resin that has recently been frequently used exhibits excellent properties required for golf balls, but has poor adhesion to other materials. To make up this disadvantage, pretreatment step for improving various adhesion property (hereinafter referred to as the “adhesion pretreatment step” or “primer coating step”) are performed after grinding. Examples of the adhesion pretreatment step include any primer coating followed by near infrared ray (NIR) drying, plasma irradiation, corona discharge treatment, etc.
Such pretreatment or step cost a great deal due to the purchase, maintenance and management of expensive equipment, the purchase of primer coatings, labor costs, etc., cause environmental problems and process losses, and also involve difficulties in control, including any environmental problems, increased process failure rates and poor quality problems.